Delta IV Heavy launches NROL-15 from Cape Canaveral

The United Launch Alliance (ULA) Delta IV rocket has made its twentieth launch Friday morning from Space Launch Complex 37B at the Cape Canaveral Air Force Station, carrying the classified NROL-15 payload for the United States National Reconnaissance Office. The launch time was 13:15 UTC (09:15 local time) – after the countdown suffered three holds in a row during the terminal count stage – two of which related to out of family Fill and Drain valve indications.Delta IV-H Launch Overview:

For the NROL-15 mission, the Delta IV, Delta 360, flew in the Heavy configuration, which consists of three Common Booster Cores (CBCs); one as the first stage and two as boosters. The Common Booster Cores are 40.8 metres (133.9 feet) long, and 5.1 metres (16.7 feet) in diameter. Each is powered by a single Pratt & Whitney Rocketdyne RS-68A engine.

The RS-68As made their maiden flight on Friday’s launch; previous flights have used the RS-68 engine. The RS-68A is an uprated variant of the RS-68, delivering increased thrust and specific impulse. The use of RS-68A engines increases the vehicle’s payload capacity.

The second stage of the Delta IV Heavy is a five-metre (16-foot) diameter Delta Cryogenic Second Stage (DCSS), which is powered by an RL10B-2 engine. The boosters, first stage and second stage all burn liquid hydrogen propellant, oxidised by liquid oxygen, making the Delta IV Heavy an all-cryogenic launch system.

Developed as part of the Evolved Expendable Launch Vehicle (EELV) programme along with the Atlas V, the Delta IV first flew on 20 November 2002, when a Delta IV Medium+(4,2) orbited the Eutelsat W5 communications satellite.

This remains the only Delta IV launch to carry a payload for a commercial organisation; all other Delta IV launches have carried US Government payloads, however three of these launches were technically commercial due to the terms of the contracts they were procured under.

The second launch occurred in March 2003, with a Delta IV in the Medium configuration carrying the penultimate Defense Satellite Communications System (DSCS) satellite into orbit, in the first orbital launch to be conducted by an all-cryogenic rocket. The Delta IV Medium and Heavy configurations are the only all-cryogenic rockets currently operational; the Medium+ configurations are not all-cryogenic as they use GEM-60 solid rocket motors to provide additional thrust during the initial stages of flight.

Five months later, the third Delta IV launched the last DSCS satellite, flying in the same configuration. For the two DSCS launches, an Integrated Apogee Boost System (IABS) upper stage was present on the rocket, however it was considered part of the payload, and not the launch system. This upper stage was used to insert the spacecraft into geosynchronous orbit after the Delta IV placed them into a transfer orbit.

In December 2004, the first Delta IV Heavy, and fourth Delta IV overall, was launched. Carrying the Heavy Lift Vehicle Operational Launch Service Demonstration Payload (HLVOLSDP) and two nanosatellites; Sparkie and Ralphie, as part of the Three-Corner Satellite (3CS) programme.

Three satellites were originally intended to be deployed, however the third, Petey, was not completed in time for the launch. Cavitation in the CBC oxidiser lines led to both boosters and the first stage cutting off prematurely after sensors incorrectly indicated that the oxidiser had been depleted.

HLVOLSDP was placed into a lower-than-planned orbit, whilst the 3CS payloads were deployed into a very low orbit, which decayed too quickly for them to return any data. This remains the Delta IV’s only launch failure to date.

A little over a month later, on 28 June, another Delta IVM+(4,2) was launched carrying the USA-184 or NROL-22 payload for the NRO. The spacecraft was placed into a Molniya orbit, and is believed to be the first in a new series of electronic intelligence (ELINT) satellites, replacing the earlier Trumpet series. This was the first Delta IV launch from Vandenberg Air Force Base in California. In November a Delta IV-M made the second launch from Vandenberg, carrying a Defense Meteorological Satellite Program (DMSP) weather satellite. This is the most recent flight of the Medium configuration to date.

This satellite has been identified as a KH-11 electro-optical imaging satellite, and operates in low Earth orbit. Another NRO satellite, NROL-27, was launched in March 2011, it is believed to be a Satellite Data System communications satellite. The last launch of 2011 occurred in July, with a second GPS satellite.

Delta 360 was the third Delta IV to launch in 2012, equalling the most flights the Delta IV has made in a calendar year. The first Delta IV launch of the year occurred in January, and carried a Wideband Global Satcom satellite into geosynchronous transfer orbit, using the M+(5,4) configuration for the second time. In April, the Medium+(5,2) configuration made its first flight, carrying the NROL-25 payload, which has been identified as a radar imaging satellite developed as part of the Future Imagery Architecture programme.

The NROL-15 payload which Delta 360 was carrying is classified, and there has been much speculation as to what type of satellite it may be.

In 2006, the US National Defense Research Institute noted in a National Security Launch Report that one NRO payload exceeded the maximum capacity of the Delta IV Heavy. This payload was not identified, however the document listed only three NRO payloads scheduled to launch on Heavy EELVs; NROL-26, NROL-15 and NROL-37. Due to the use of RS-68A engines, and hence Delta 360’s increased payload capacity, it has been suggested that NROL-15 may be the launch in question.

The mission’s out-of-sequence launch designation has also led to speculation that NROL-15 may have been delayed many years, and that it might have originally been intended to fly aboard a Titan IV. NROL-15 is the lowest-numbered NRO mission that has not already been launched, and one of only two missions with designations below NROL-30 that have not yet flown – the other, NROL-29, is believed to have been cancelled.

NROL-15 was the thirty-fifth launch to fly with an NRO Launch, or NROL, designation, a practise which began in late 1996 when the NRO started to acknowledge the launches of its spacecraft publicly. It is unclear how the designations are assigned, but no two consecutive NROL designations launched to date have been assigned to the same type of payload. Early launches were mostly in sequence, however later launches have been far less sequential; for example in 2011 NROL-49 was launched, followed by NROL-66, NROL-27 and NROL-34.

The launch of NROL-15 comes almost 11 years after that of NROL-14; a KH-11 imaging satellite, and seven years after the launch of NROL-16, a Lacrosse radar imaging satellite. NROL-16 was itself fairly late compared to similarly-numbered launches. It has been unusual for a single mission to launch more than a few years after those around it, although it is not unheard of; NROL-1 was not launched until eight years after the designation system was first introduced.

The launch hazard areas for Delta 360 show that the rocket was heading due east from Cape Canaveral, presumably towards a geosynchronous orbit. Its payload is most likely to be a geosynchronous electronic intelligence (ELINT) satellite, of the same type as NROL-26 and NROL-32. These satellites are rumoured to be named Mentor, however it is not known whether this is true, and if it is the NRO has probably already changed the programme name. They are also known as Advanced Orion.

The payload fairing which encapsulates the satellite supports it being a Mentor satellite; Delta 360 is fitted with a metallic trisector fairing, which is essentially the same fairing that was used by the Titan IV rocket. It has a diameter of 5.8 metres (200 inches), and is 19.8 metres (65 feet) long; 70 centimetres (2.3 feet) longer than the composite bisector fairing which was designed for the Delta IV.

The metallic fairing has been used on three of the previous Delta IV Heavy launches; DSP-24, NROL-26 and NROL-32. The composite fairing was used for the demonstration launch, and NROL-49.

If NROL-15 is a Mentor satellite, it will be the sixth to be launched, and the third since 2008. Mentor is the United States’ third-generation geosynchronous ELINT system. The first-generation system, Rhyolite (later Aquacade), consisted of four satellites launched using Atlas SLV-3A Agena-D carrier rockets between 1970 and 1978.

The first Mentor satellite, USA-110, was launched in May 1995 on a Titan IV(401)A. The second, USA-139 or NROL-6, followed in May 1998 on a Titan IV(401)B, and the third, USA-171 or NROL-19, was launched in September 2003 also on a Titan IVB. USA-202, or NROL-26, was the fourth Mentor to be launched, and was carried to orbit by a Delta IV Heavy in 2008, with USA-223 or NROL-32 following in 2010.

USA-110 was last known to be located at 127 degrees East, USA-139 was located at 44 degrees east for most of its operational life, moving to 14.5 degrees West after USA-202 replaced it in 2009. The last known location of USA-171 was 95.5 degrees east.

Details on the deployment of Mentor satellites are somewhat unclear since both USA-110 and USA-171 operate over areas where no amateur observers are present to track them. Given the lack of observations, USA-223 is probably also positioned over an area with no amateur observers; given the age of USA-110 it is likely that USA-223 was its replacement. NROL-15 may complete the renewal of the constellation by replacing USA-171, however this is not entirely clear as USA-171 is a much younger spacecraft than the other two.

An alternative theory is that NROL-15 is carrying a Misty imaging satellite. The Misty programme was reported to have been discontinued around 2007, however it could have since been revived, or if a spacecraft was already under construction, the NRO may still have proceeded with it. Misty, which is believed to be one of the largest and most expensive satellites ever developed is a stealth imaging satellite reportedly derived from the KH-11. Two have been launched to date; USA-53 and USA-144.

USA-53 was deployed by Space Shuttle Atlantis in March 1990, during STS-36, into an orbit with an inclination of 62 degrees, and an altitude of around 254 kilometres (158 statute miles, 137 nautical miles). Four days after deployment from Atlantis, the spacecraft was reported to have disintegrated, with five pieces of debris being catalogued. It remains unclear whether the debris was a deliberate decoy, or whether it served a purpose, such as lens covers.

In October 1990, the satellite was discovered to still be in orbit and intact, when it was located in an orbit at an altitude of 811 kilometres (504 statute miles, 438 nautical miles), and an inclination of 65 degrees. It was not observed again until 1996, when an unidentified satellite was found in an orbit with 728 kilometres (452 statute miles, 393 nautical miles) altitude, and 66.2 degrees inclination.

The long periods during which the satellite went undetected have been attributed to the satellite exhibiting stealth characteristics, however it is believed the satellite had to maintain a specific orientation to remain stealthy, which allowed it to be observed occasionally. USA-53 is believed to have been deorbited, but this has never been confirmed.

USA-144 was launched in May 1999, atop a Titan IV(404)B. Like USA-53, it shed debris, then it appeared to manoeuvre into a higher orbit, with a perigee of 2,705 kilometres (1,681 statute miles, 1,461 nautical miles), an apogee of 3,129 kilometres (1,944 statute miles, 1,670 nautical miles), and 63.4 degrees of inclination. This unusual orbit confused observers, leading to it being identified as a technology demonstration satellite, part of the apparently-cancelled Enhanced Imaging System or 8X programme, or even an SDS satellite which had failed to inject itself into Molniya orbit.

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It was later discovered from its orbital perturbations that it had a very low density, suggesting that it was actually a decoy. The real payload has never been observed, and is widely believed to have been a second Misty satellite. Its status is unknown.

Delta 360’s launch azimuth is not consistent with a Misty launch; imaging satellites typically require high-inclination orbits; the previous Misty satellites operated at around 65 degrees, and NROL-15 is launching to an orbit with an inclination of no more 28.5 degrees. Some observers believe that after leaving the launch hazard area, the rocket will manoeuvre to increase its orbit’s inclination, allowing a Misty satellite to be deployed while giving the impression the rocket is heading for a geosynchronous orbit.

Another theory is that Misty would be deployed into a 28.5 degree orbit and use its own propulsion system to increase its inclination, while Delta 360’s upper stage continues to geosynchronous orbit with a decoy payload.

It is unlikely that, even with the engine upgrade, a Delta IV Heavy could accomplish either of these missions. That said, given that the Delta IV Heavy has launched Mentor satellites before, if NROL-15 is a Mentor it would not explain the need for the uprated engines. The satellite could feature new enhancements which increase its mass, or be a new variant. It is more likely, however, that the engine modification is just a coincidence.

If NROL-15 does replace the last of the original three Mentors, it is unlikely that another satellite would need to be launched until at least the end of the decade. This being the case, NROL-37 could be the payload which was reported to be too heavy for the Delta IV to launch. Given the age of the series, it is therefore quite possible that NROL-15 would be the last Mentor.

Details of Delta 360’s mission profile have not been made public, however it has been reported that Delta 310, the demonstration launch, was to have flown the same mission profile used to deploy Mentor satellites. If the payload is Misty, the flight would follow a very different profile.

Regardless of the mission, the profile shows the ignition of the CBC engines will occur five and a half seconds before launch, with liftoff occurring at T-0. Delta 360 will fly downrange due east from Cape Canaveral, over the Atlantic Ocean. Fifty seconds after liftoff, the core CBC will throttle down, with the vehicle passing through max-Q half a minute later, closely followed by it achieving supersonic speed.

A roll manoeuvre will occur approximately 150 seconds after liftoff, with Delta 360 assuming an attitude with all three CBCs level. The two strap-on CBCs will begin to throttle down at T+230 seconds, before burning out 245 seconds after launch, and being jettisoned three seconds later. A second after separation, the core stage will throttle up. Around seventy seconds after throttle-up, the engine will again throttle down in preparation for burnout.

The first stage will end its burn about five minutes, 33 seconds after liftoff, with stage separation occurring seven and a half seconds later. The vehicle will coast for a further 13.5 seconds after staging, during which time the engine nozzle will be extended. At the end of the coast, the RL10 engine will ignite. Ten seconds later, the fairing will separate, and official coverage of the mission will end. The second stage’s first burn will probably last around seven minutes, placing the payload into a parking orbit.

If the payload is destined for geosynchronous orbit, the second stage will restart about seven minutes and 40 seconds later, for an eight minute burn to reach a transfer orbit. A five hour coast phase will follow, allowing the upper stage and payload to drift towards the apogee of their orbit, before ignition for a third and final burn, lasting about three and a quarter minutes, to raise the perigee to geosynchronous altitude.

A launch to a higher-inclination low Earth orbit would probably require two or three burns of the second stage; the first being similar to the first burn for the geosynchronous profile, while the second and third will raise the orbit’s apogee, perigee, and particularly inclination.

Delta 360 flew from Space Launch Complex 37B (SLC-37B) at Cape Canaveral, a launch complex which was originally built as a backup pad for the Saturn I in the 1960s.

It was used for eight launches which supported the Apollo programme, including Apollo 5, the first test flight of the Lunar Module. Six Saturn Is and two Saturn IBs launched from the complex between 1964 and 1968, after which the pad was mothballed, in anticipation that it would be reactivated when Saturn IB launches resumed for low Earth orbit programmes after the moon landings.

Instead, the Apollo Applications programme was scaled back, and Launch Complex 39 was modified to accommodate the Saturn IB by means of the “Milkstool” adaptor which allowed a Saturn IB to use a Launch Umbilical Tower that had originally been designed for the larger Saturn V. The original complex was demolished in the 1970s.

Construction of the new complex began in the late 1990s, with the first Delta IV launch from the pad occurring in 2002. Delta 360 was the sixteenth Delta IV to launch from SLC-37B. Another pad, LC-37A, was part of the original complex, however it was never used, and only pad B was rebuilt for the Delta IV.

Delta 360 was launched by United Launch Alliance; a company which was formed in late 2006, and took over operation of Boeing’s Delta II and Delta IV rockets, as well as Lockheed Martin’s Atlas V. Including NROL-15, United Launch Alliance will have conducted 13 of the Delta IV’s 20 flights.

The next Delta IV launch is planned for October, carrying a Global Positioning System navigation satellite. Before that, ULA will launch two Atlas Vs; one carrying the NROL-36 payload for the NRO, and the other carrying NASA’s Radiation Belt Storm Probes. Both of these launches are currently scheduled for August.

NROL-36 is also the next scheduled launch of an NRO payload. The next Delta IV Heavy launch is scheduled for next August, carrying NROL-65, which is expected to be a KH-11 imaging satellite.